Open circuit diagnostic for pulsed solenoid I/P

Abstract

Techniques for diagnosing failures in a digital solenoid I/P converter are provided herein. A controller of the I/P converter may apply a fixed voltage to an I/P coil of the I/P converter, causing an armature to move from an off-position to an on-position in a properly-functioning I/P converter. The controller may receive an indication of whether a digital logic line trip has occurred, indicating that a current for the I/P coil has reached a desired maximum current level. The controller may remove the fixed voltage applied to the I/P coil when the maximum current level is reached or when a threshold period of time has elapsed from the application of the fixed voltage to the I/P coil. The controller may diagnose, based on whether the digital logic line trip occurred prior to removing the fixed voltage, a failure in the I/P converter.

What is claimed is: 
     
       1. A method for diagnosing failures in a digital solenoid I/P converter of a field device in a process control system, wherein the digital solenoid I/P converter includes an I/P coil and drive circuitry, and wherein the digital solenoid I/P converter, when actuated, causes an armature to move from an off-position to an on-position, the method comprising:
 establishing that a fixed voltage has been applied to the I/P coil at a first time; 
 establishing that the fixed voltage was removed from the I/P coil at a second time; 
 receiving, from a current sensor, an indication of a current level associated with the I/P coil; 
 performing a first comparison of the indication of the current level associated with the I/P coil and a desired maximum current level; 
 causing, based on the comparison, a digital logic line to trip when the current level associated with the I/P coil reaches the desired maximum current level; 
 performing a second comparison of whether the digital logic line trips before the second time; 
 determining, based on the second comparison, whether the I/P coil and drive circuitry are properly functioning or whether one or more of the I/P coil or the drive circuitry has failed; and 
 causing a controller to take a control action changing an operation of the process control system based on determining that one or more of the I/P coil or the drive circuitry has failed, wherein the control action includes switching from using the field device in the process control system to using a second, redundant field device in the process control system. 
 
     
     
       2. The method of  claim 1 , wherein determining whether the I/P coil and drive circuitry are properly functioning or whether one or more of the I/P coil or the drive circuitry has failed further comprises:
 determining, based on the digital logic line tripping before the second time, that the I/P coil and drive circuitry are properly functioning. 
 
     
     
       3. The method of  claim 1 , wherein determining whether the I/P coil and drive circuitry are properly functioning or whether one or more of the I/P coil or the drive circuitry has failed:
 determining, based on the digital logic line not tripping before the second time, that one or more of the I/P coil or the drive circuitry has failed. 
 
     
     
       4. The method of  claim 3 , further comprising determining, based on the digital logic line not tripping before the second time, that one or more of the I/P coil or the drive circuitry has failed due to an open circuit in one or more of the I/P coil or the drive circuitry. 
     
     
       5. The method of  claim 3 , further comprising:
 generating an alert based on determining that one or more of the I/P coil or the drive circuitry has failed. 
 
     
     
       6. A system for diagnosing failures in a digital solenoid I/P converter in a process control system, the system comprising:
 a digital solenoid I/P converter of a field device of the process control system, including an I/P coil and drive circuitry, the digital solenoid I/P converter being configured to cause an armature to move from an off-position to an on-position when actuated; 
 a controller configured to cause a fixed voltage to be applied to the I/P coil at a first time and to remove the fixed voltage applied to the I/P coil at a second time, when the first of the following occurs: (i) the I/P coil reaches the desired maximum current level; or (ii) a threshold period of time has elapsed from the first time; 
 a current sensor configured to sense an amount of current associated with the I/P coil; and 
 a diagnostic circuit configured to:
 perform a first comparison of the sensed amount of current associated with the I/P coil and a maximum desired current level; 
 cause, based on the first comparison, a digital logic line to trip when the sensed amount of current associated with the I/P coil reaches the maximum desired current level; 
 perform a second comparison of whether the digital logic line has tripped after the first time; 
 determine, based on the second comparison, whether the I/P coil and drive circuitry are properly functioning or whether one or more of the I/P coil or the drive circuitry has failed; and 
 cause the controller to take a control action changing an operation of the process control system based on determining that one or more of the I/P coil or the drive circuitry has failed, wherein the control action includes switching from using the field device in the process control system to using a second, redundant field device in the process control system. 
 
 
     
     
       7. The system of  claim 6 , wherein the diagnostic circuit is configured to determine, based on the digital logic line tripping before the second time, that the I/P coil and drive circuitry are properly functioning. 
     
     
       8. The system of  claim 6 , wherein the diagnostic circuit is configured to determine, based on the digital logic line not tripping before the second time, that one or more of the I/P coil or the drive circuitry has failed. 
     
     
       9. The system of  claim 8 , wherein the diagnostic circuit is configured to determine, based on the digital logic line not tripping before the second time, that one or more of the I/P coil or the drive circuitry has failed due to an open circuit in one or more of the I/P coil or the drive circuitry. 
     
     
       10. The system of  claim 8 , wherein the diagnostic circuit is further configured to generate an alert based on determining that one or more of the I/P coil or the drive circuitry has failed.